1. Field of the Invention
The present invention relates to an image capturing apparatus, a control method, and a recording medium, and particularly to, a technique of generating a moving image using a composite image obtained by combining a plurality of images as a frame.
2. Description of the Related Art
In general, the tonal range (dynamic range) of an image sensor such as a CCD or CMOS sensor used for an image capturing apparatus such as a digital camera is narrower than the tonal range of a silver halide film. A narrow range may lead to blown-out highlight on a high-luminance subject or shadow-detail loss on a low-luminance subject in a captured image obtained by image capturing depending on an image capturing environment.
Recently, there is available an image capturing apparatus using such an image sensor, which generates a so-called HDR (High Dynamic Range) image with an enhanced tonal range by combining a plurality of images obtained by image capturing of a subject at different exposures. The generation of an HDR image uses, for example, an intermediate-exposure image captured at an exposure set as a proper exposure for a subject, a high-exposure image captured at an exposure leading to overexposure, and a low-exposure image captured at an exposure leading to underexposure (Japanese Patent Publication No. 7-97841).
An image correction technique of combining a plurality of images obtained by image capturing of the same subject as in the case of the generation of an HDR image is also used for, for example, a camera shake compensation technique. Note that in such an image correction technique, all the images need to be obtained in advance by image capturing of a subject at the same angle of view.
The above image correction technique can be applied to moving image capturing as well as still image capturing. That is, it is possible to generate, for example, a moving image (HDR moving image) with an enhanced tonal range by using, as a final moving image frame, an image obtained by combining a plurality of frames of a captured moving image.
In moving image capturing, when selecting frames to be used for combining operation according to a predetermined rule, the selected frames sometimes differ in angle of view. That is, in moving image capturing, frames may differ in angle of view due to the zooming operation performed by the operator. For this reason, the moving image obtained by generating frames using the above image correction technique may have portions with different image qualities within a frame or exhibit different image qualities between frames.